At the most basic level, you only need a load resistor. The CT will be a current source whose full-scale value depends on the turns ration to the primary. You have 1A in the primary. So if you have 100 turns in the CT, you should get 0.01A full scale out of the CT. Then, just choose a resistor that will give you a voltage across it equal to the full-scale of you uC ADC when 0.01A flows through it.

This is a neat circuit that I developed that works really well. I eliminated the burden resistor and replaced it with active feedback. There is always 0V across the secondary, and U408B transimpedance amp drives a current that cancels the flux generated by the primary.

This has the benefit of removing non-linearities due to changing magnetic flux density in the core (it is always 0) and magnetic hysteresis.

As the best hit in three pages of google results for "current transformer burden resistor calculation", this thread is something of a public resource. It's a clever circuit and has wider application with different CTs. For example, but eliminating the magnetic flux with active feedback, it seems to me much smaller CTs could be used than in burden resistor designs - not?

As the best hit in three pages of google results for "current transformer burden resistor calculation", this thread is something of a public resource. It's a clever circuit and has wider application with different CTs. For example, but eliminating the magnetic flux with active feedback, it seems to me much smaller CTs could be used than in burden resistor designs - not?

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Ha! I am famous!

I appreciate you recognizing the value of the concept. I mistook your original query as implying that I was doing it wrong -- which flummoxed me, as the circuit has been in production for many years.

The advantage to me is the increase in accuracy and dynamic range over a standard CT configuration. I am sure there are other benefits.

I am an inventor (with patents). I try lots of things that others wouldn't consider. Sometimes I come up with something valuable -- maybe this is one of them. Let me know if/where you go with it.